The actor Robert Downey Jr has called Channel 4’s Krishnan Guru-Murthy a “syphilitic parasite” and a “bottom-feeding muckraker” days after walking out of an interview with him.

His comments came during an interview on the Howard Stern Show on US radio. Downey Jr, who is reprising his role as Tony Stark / Iron Man in new Marvel film Avengers: Age of Ultron said: “I’m one of those guys who I’m always assuming the social decorum is in play, and that we’re promoting a superhero movie, a lot of kids are going to see it, and that just has nothing to do with your creepy dark agenda.”

Addressing Guru-Murthy, he added: “You know what? You are a bottom-feeding muckraker.”

He went on: “What I have to do in the future is give myself permission to say, ‘That is more than likely a syphilitic parasite and I need to distance myself from this clown’. Otherwise I’m probably gonna put hands on this somebody and then there’s a real story!”

He also told Stern “I just wish I’d left sooner.”

Guru-Murthy took to Twitter to brush off the comments, joking, “I think that might just be actionable. Do u think he’s worth much?”

@TelegraphFilm I think that might just be actionable. Do u think he’s worth much?

Downey Jr called time on the interview after Guru-Murthy strayed off the topic of his new film, and on to questions about the actor’s past, grilling him over whether he was a liberal or not. Downey Jr responded ““I couldn’t even really tell you what a liberal is… Are we promoting a movie?” before describing himself as apolitical.

Guru-Murthy is making quite a name for himself as a controversial interviewer. In 2013 he asked filmmaker Quentin Tarantino “why are you so sure that there is no link between enjoying movie violence and enjoying real violence?” Tarantino refused to answer the question telling Guru-Murthy: “I’m not your slave and you’re not my master. I’m here to sell my movie. This is a commercial for the movie, make no mistake.”